Clocked full-rail differential logic with sense amplifiers

ABSTRACT

Modified full-rail differential logic circuits are activated by a delayed clock and include a sense amplifier circuit that is triggered by a second delayed clock. The addition of the sense amplifier circuit, and second delayed clock signal allows the sense amplifier circuit to act as the driver and therefore there is no need for increasing the size of the differential logic network to provide a driver function. Consequently, the modified full-rail differential logic circuits of the invention are capable of operating efficiently under heavy load conditions without the increased size and the significant reduction in speed associated with prior art full-rail differential logic circuits.

FIELD OF THE INVENTION

The present invention relates generally to logic circuits and, moreparticularly, to full-rail differential logic circuits.

BACKGROUND OF THE INVENTION

One example of a prior art full-rail differential logic circuit ispresented and discussed at page 112, and shown in FIG. 3(c), in “HIGHSPEED CMOS DESIGN STYLES” by Bernstein et al. of IBM Microelectronics;Kluwer Academic Publishers, 101 Philip Drive, Assinippi Park, Norwell,Mass., 02061; ISBN 0-7923-8220-X, hereinafter referred to as theBernstein et al. reference, which is incorporated herein by reference,in its entirety, for all purposes.

FIG. 1 shows a prior art full-rail differential logic circuit 100similar to that discussed in the Bernstein et al. reference. As seen inFIG. 1, prior art full-rail differential logic circuit 100 included sixtransistors: PFET 105, PFET 107, NFET 109, PFET 115, PFET 117 and NFET121. Prior art full-rail differential logic circuit 100 also included:differential logic 123 with inputs 151 and 153; out terminal 111; andoutBar terminal 113. Prior art full-rail differential logic circuit 100is activated from a delayed clock signal CLKA. As shown in FIG. 1,signal CLKA was supplied to: gate 116 of PFET 115; gate 118 of PFET 117;gate 129 of NFET 109; and gate 122 of NFET 121.

Prior art full-rail differential logic circuit 100 worked reasonablywell under conditions of a light load, for instance under conditionswhere fan out is less than four. However, prior art full-raildifferential logic circuit 100 was less useful under conditions of aheavy load, for instance, in cases where fan out exceeded four. Theshortcomings of prior art full-rail differential logic circuit 100 aroseprimarily because under heavy load conditions logic network 123 had tobe increased in size to act as a driver for the next stage in thecascade. This in turn meant that logic network 123 was large, slow andinefficient. The problem was further aggravated as additional prior artfull-rail differential logic circuits 100 were cascaded together to formthe chains commonly used in the industry. Consequently, the fullpotential of prior art full-rail differential logic circuits 100 was notrealized and their use was narrowly limited to light load applications.

What is needed is a method and apparatus for creating full-raildifferential logic circuits that are capable of efficient use underheavy loads and are therefore more flexible, more space efficient andmore reliable than prior art full-rail differential logic circuits.

SUMMARY OF THE INVENTION

The modified full-rail differential logic circuits of the inventioninclude a sense amplifier circuit that is triggered by the delayed clockof the following stage, i.e., the clock input to the sense amplifiercircuit of the modified full-rail differential logic circuits of theinvention is additionally delayed with respect to the delayed clock thatdrives the full-rail differential logic. The addition of the senseamplifier circuit, and second delayed clock signal, according to theinvention, allows the sense amplifier circuit to act as the driver andtherefore there is no need for increasing the size of the logic networkto provide the driver function. Consequently, the modified full-raildifferential logic circuits of the invention are capable of operatingefficiently under heavy load conditions without the increased size andthe significant reduction in speed associated with prior art full-raildifferential logic circuits. In addition, the modified full-raildifferential logic circuits of the invention require less space, aresimpler, dissipate less heat and have fewer components to potentiallyfail.

The modified full-rail differential logic circuits of the invention canbe cascaded together to form the chains commonly used in the industry.When the modified full-rail differential logic circuits of the inventionare cascaded together, the advantages of the modified full-raildifferential logic circuits of the invention are particularly evidentand the gains in terms of efficiency, size reduction and flexibility arefurther pronounced.

In particular, one embodiment of the invention is a cascaded chain ofmodified full-rail differential logic circuits. The chain includes afirst modified full-rail differential logic circuit. The first modifiedfull-rail differential logic circuit includes: a first modifiedfull-rail differential logic circuit first clock input terminal; atleast one first modified full-rail differential logic circuit data inputterminal; at least one first modified full-rail differential logiccircuit data output terminal; and a first modified full-raildifferential logic circuit second clock input terminal.

The cascaded chain of the invention also includes a second modifiedfull-rail differential logic circuit. The second modified full-raildifferential logic circuit includes: a second modified full-raildifferential logic circuit first clock input terminal; at least onesecond modified full-rail differential logic circuit data inputterminal; at least one second modified full-rail differential logiccircuit data output terminal; and a second modified full-raildifferential logic circuit second clock input terminal.

According to the invention, the at least one first modified full-raildifferential logic circuit data output terminal is coupled to the atleast one second modified full-rail differential logic circuit datainput terminal to form the chain. According to the invention, a firstclock signal is coupled to the first modified full-rail differentiallogic circuit first clock input terminal and a second clock signal iscoupled to the first modified full-rail differential logic circuitsecond clock input terminal and the second modified full-raildifferential logic circuit first clock input terminal. According to theinvention, the second clock signal is delayed with respect to the firstclock signal by a predetermined delay time.

In one embodiment of the invention, a delay circuit is coupled betweenthe first modified full-rail differential logic circuit clock inputterminal and the second modified full-rail differential logic circuitfirst clock input terminal to provide the predetermined delay time. Inone embodiment of the invention, the delay circuit is also coupledbetween the first modified full-rail differential logic circuit clockinput terminal and the first modified full-rail differential logiccircuit second clock input terminal to provide the predetermined delaytime.

One embodiment of the invention is a modified full-rail differentiallogic circuit that includes a modified full-rail differential logiccircuit out terminal and a modified full-rail differential logic circuitoutBar terminal.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a first node, the first node is coupled to afirst supply voltage.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a first transistor, the first transistorincluding a first transistor first flow electrode, a first transistorsecond flow electrode and a first transistor control electrode. Thefirst node is coupled to the first transistor first flow electrode andthe first transistor second flow electrode is coupled to the modifiedfull-rail differential logic circuit out terminal. The first transistorcan also include a back bias input terminal having a back bias voltagethereon.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a second transistor, the second transistorincluding a second transistor first flow electrode, a second transistorsecond flow electrode and a second transistor control electrode. Thefirst node is coupled to the second transistor first flow electrode andthe second transistor second flow electrode is coupled to the modifiedfull-rail differential logic circuit outBar terminal.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a third transistor, the third transistorincluding a third transistor first flow electrode, a third transistorsecond flow electrode and a third transistor control electrode. Thefirst transistor control electrode is coupled to the third transistorfirst flow electrode and the modified full-rail differential logiccircuit outBar terminal. The second transistor control electrode iscoupled to the third transistor second flow electrode and the modifiedfull-rail differential logic circuit out terminal. The third transistorcontrol electrode is coupled to a clock signal CLKA.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a fourth transistor, the fourth transistorincluding a fourth transistor first flow electrode, a fourth transistorsecond flow electrode and a fourth transistor control electrode. Thefirst node is coupled to the fourth transistor first flow electrode andthe fourth transistor second flow electrode is coupled to the modifiedfull-rail differential logic circuit out terminal. The fourth transistorcontrol electrode is coupled to the clock signal CLKA. The fourthtransistor can also include a back bias input terminal having a backbias voltage thereon.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a fifth transistor, the fifth transistorincluding a fifth transistor first flow electrode, a fifth transistorsecond flow electrode and a fifth transistor control electrode. Thefirst node is coupled to the fifth transistor first flow electrode andthe fifth transistor second flow electrode is coupled to the modifiedfull-rail differential logic circuit outBar terminal. The fifthtransistor control electrode is coupled to the clock signal CLKA. Thefifth transistor can also include a back bias input terminal having aback bias voltage thereon.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a sense amplifier circuit coupled betweenthe modified full-rail differential logic circuit out terminal and themodified full-rail differential logic circuit outBar terminal.

In one embodiment of the invention, the modified full-rail differentiallogic circuit sense amplifier circuit includes a sixth transistor, thesixth transistor including a sixth transistor first flow electrode, asixth transistor second flow electrode and a sixth transistor controlelectrode. The first transistor second flow electrode is coupled to thesixth transistor first flow electrode. The sixth transistor second flowelectrode is coupled to a second node. The sixth transistor controlelectrode is coupled to the third transistor first flow electrode andthe modified full-rail differential logic circuit outbar terminal.

In one embodiment of the invention, the modified full-rail differentiallogic circuit sense amplifier circuit also includes a seventhtransistor, the seventh transistor including a seventh transistor firstflow electrode, a seventh transistor second flow electrode and a seventhtransistor control electrode. The second transistor second flowelectrode is coupled to the seventh transistor first flow electrode. Theseventh transistor second flow electrode is coupled to the second node.The seventh transistor control electrode is coupled to the thirdtransistor second flow electrode and the modified full-rail differentiallogic circuit out terminal.

In one embodiment of the invention, the modified full-rail differentiallogic circuit sense amplifier circuit also includes an eighthtransistor, the eighth transistor including an eighth transistor firstflow electrode, an eighth transistor second flow electrode and an eighthtransistor control electrode. The eighth transistor first flow electrodeis coupled to the second node and the eighth transistor second flowelectrode is coupled to a second supply voltage. A clock signal CLKB iscoupled to the eighth transistor control electrode of the modifiedfull-rail differential logic circuit sense amplifier circuit. In oneembodiment of the invention, the clock signal CLKB is delayed apredetermined time with respect to the clock signal CLKA.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a logic block, the logic block including atleast one logic block input terminal, a logic block out terminal and alogic block outbar terminal. The logic block out terminal is coupled tothe modified full-rail differential logic circuit out terminal and thelogic block outBar terminal is coupled to the modified full-raildifferential logic circuit outBar terminal.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a ninth transistor, the ninth transistorincluding a ninth transistor first flow electrode, a ninth transistorsecond flow electrode and a ninth transistor control electrode. Theninth transistor first flow electrode is coupled to the logic block. Theninth transistor control electrode is coupled to the clock signal CLKA.The ninth transistor second flow electrode is coupled to the secondsupply voltage.

As discussed in more detail below, the modified full-rail differentiallogic circuits of the invention are capable of efficient use under heavyloads and are therefore more flexible, more space efficient and morereliable than prior art full-rail differential logic circuits.

It is to be understood that both the foregoing general description andfollowing detailed description are intended only to exemplify andexplain the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in, and constitute apart of this specification, illustrate embodiments of the invention and,together with the description, serve to explain the advantages andprinciples of the invention. In the drawings:

FIG. 1 shows a schematic diagram of a prior art full-rail differentiallogic;

FIG. 2 shows a schematic diagram of one embodiment of a modifiedfull-rail differential logic circuit designed according to theprinciples of the present invention;

FIG. 3 shows one embodiment of a cascaded chain of modified full-raildifferential logic circuits according to the principles of the presentinvention; and

FIG. 4 is a one embodiment of a timing diagram for the cascaded chain ofmodified full-rail differential logic circuits of the invention shown inFIG. 3.

DETAILED DESCRIPTION

The invention will now be described in reference to the accompanyingdrawings. The same reference numbers may be used throughout the drawingsand the following description to refer to the same or like parts.

The modified full-rail differential logic circuits (200 in FIG. 2 and300A, 300B, 300C and 300N in FIG. 3) of the invention include a senseamplifier circuit (280 in FIG. 2) that is triggered by the delayed clock(CLKB in FIG. 2 and FIG. 3 and CLKC, CLKD, CLKN+1 in FIG. 3) of thefollowing stage, i.e., the clock input to the sense amplifier circuit ofthe modified full-rail differential logic circuits of the invention isadditionally delayed with respect to the delayed clock that drives thefull-rail differential logic. The addition of the sense amplifiercircuit and second delayed clock signal, according to the invention,allows the sense amplifier circuit to act as the driver and thereforethere is no need for increasing the size of the logic network (123 inFIG. 2) to provide the driver function. Consequently, the modifiedfull-rail differential logic circuits of the invention are capable ofoperating efficiently under heavy load conditions without thesignificant reduction in speed associated with prior art full-raildifferential logic circuits. In addition, the modified full-raildifferential logic circuits of the invention require less space, aresimpler, dissipate less heat and have fewer components to potentiallyfail.

The modified full-rail differential logic circuits of the invention canbe cascaded together to form the chains (301 in FIG. 3) commonly used inthe industry. When the modified full-rail differential logic circuits ofthe invention are cascaded together, the advantages of the modifiedfull-rail differential logic circuits of the invention are particularlyevident and the gains in terms of efficiency, size reduction andflexibility are further pronounced.

FIG. 2 shows a schematic diagram of one embodiment of a modifiedfull-rail differential logic circuit 200 designed according to theprinciples of the present invention. As seen in FIG. 2, modifiedfull-rail differential logic circuit 200 includes a first supply voltage202 coupled to a first node 201. First node 201 is coupled to: a source206 of a first transistor, PFET 205; a source 208 of a secondtransistor, PFET 207; a source 242 of a fourth transistor, PFET 241 anda source 247 of a fifth transistor, PFET 246. The clock signal CLKA iscoupled to: a control electrode or gate 245 of PFET 241; a controlelectrode or gate 249 of PFET 246; a control electrode or gate 229 of athird transistor, NFET 209; a control electrode or gate 263 of a ninthtransistor, NFET 260.

A control electrode or gate 216 of PFET 205 is coupled to a source 240of NFET 209 and an outBar terminal 213. A control electrode or gate 214of PFET 207 is coupled to a drain 238 of NFET 209 and an out terminal211. A drain 210 of PFET 205 is coupled to out terminal 211 and a drain212 of PFET 207 is coupled to outBar terminal 213.

As discussed above, gate 245 of PFET 241 is coupled to clock signalCLKA, as is gate 249 of PFET 246. A drain 243 of PFET 241 is coupled toout terminal 211 and a drain 248, of PFET 249 is coupled to outBarterminal 213.

According to the invention, modified full-rail differential logiccircuit 200 also includes sense amplifier circuit 280. In one embodimentof the invention, sense amplifier circuit 280 includes a sixthtransistor, NFET 215 including a drain 251, a source 253 and a controlelectrode or gate 252. Drain 210 of PFET 205 is coupled to drain 251 ofNFET 215. Source 253 of NFET 215 is coupled to a second node 255. Gate252 of NFET 215 is coupled to source 240 of NFET 209 and modifiedfull-rail differential logic circuit outBar terminal 213.

In one embodiment of the invention, sense amplifier circuit 280 alsoincludes a seventh transistor, NFET 217 including a drain 259, a source257 and a control electrode or gate 258. Drain 212 of PFET 207 iscoupled to drain 259 of NFET 217. Source 257 of NFET 217 is coupled to asecond node 255. Gate 258 of NFET 217 is coupled to drain 238 of NFET209 and modified full-rail differential logic circuit out terminal 211.

In one embodiment of the invention, sense amplifier circuit 280 ofmodified full-rail differential logic circuit 200 also includes aneighth transistor, NFET 270, including a drain 218, a source 221 and acontrol electrode or gate 227. Drain 218 of NFET 270 is coupled tosecond node 255. Source 271 of NFET 270 is coupled to a second supplyvoltage 271. A delayed clock signal CLKB is coupled to control electrodeor gate 227 of NFET 270. According to one embodiment of the invention,clock signal CLKB is delayed with respect to clock signal CLKA by apredetermined time.

In one embodiment of the invention, the modified full-rail differentiallogic circuit also includes a logic block 223. In one embodiment of theinvention, logic block 223 is an NMOS pass transistor logic networkincluding input terminals 251 and 253. A logic block out terminal 278 iscoupled to out terminal 211 and a logic block outBar terminal 279 iscoupled to outBar terminal 213. In other embodiments of the invention,logic block 223 includes any type of differential logic and/or circuitryused in the art including various logic gates, logic devices andcircuits.

A particular embodiment of a modified full-rail differential logiccircuit 200 according to the invention is shown in FIG. 2. Those ofskill in the art will recognize that modified full-rail differentiallogic circuit 200 can be easily modified. For example, differenttransistors, i.e., PFETs 205, 207, 241, and 246 or NFETs 209, 215, 217,260 and 270 can be used. In particular, the NFETs and PFETS shown inFIG. 2 can be readily exchanged for PFETs and NFETs by reversing thepolarities of the supply voltages 202 and 271, or by other well knowncircuit modifications. Consequently, the modified full-rail differentiallogic circuit 200 that is shown in FIG. 2 is simply one embodiment ofthe invention used for illustrative purposes only and does not limit thepresent invention to that one embodiment of the invention.

As discussed above, modified full-rail differential logic circuit 200 ofthe invention includes sense amplifier circuit 280 that is triggered bydelayed clock signal CLKB of the following stage, i.e., the clock signalCLKB to gate 227 of NFET 270 of sense amplifier circuit 280 isadditionally delayed with respect to the delayed clock signal CLKA.Clock signal CLKA is coupled to: gate 245 of PFET 241; gate 229 of NFET209; gate 249 of PFET 246 and gate 263 of NFET 260. The addition ofsense amplifier circuit 280 and second delayed clock signal CLKB,according to the invention, allows sense amplifier circuit 280 to act asthe driver and therefore there is no need for increasing the size of thelogic block 223 to provide the driver function. Consequently, modifiedfull-rail differential logic circuit 200 of the invention is capable ofoperating efficiently under heavy load conditions without thesignificant reduction in speed associated with prior art full-raildifferential logic circuits 100. In addition, modified full-raildifferential logic circuit 200 requires less space, is simpler,dissipates less heat and has fewer components to potentially fail.

As also discussed above, modified full-rail differential logic circuit200 can be cascaded together with other modified full-rail differentiallogic circuits 200 to form the chains commonly used in the industry.When modified full-rail differential logic circuits 200 of the inventionare cascaded together, the advantages of modified full-rail differentiallogic circuit 200 is particularly evident and the gains in terms ofefficiency, size reduction and flexibility are further pronounced.

When modified full-rail differential logic circuits 200 of the inventionare cascaded together, the delayed clock signal CLKA is, according tothe invention, timed to be at least the delay of the previous modifiedfull-rail differential logic circuit 200 (not shown) to ensure eachmodified full-rail differential logic circuit 200 of the invention isswitched or “fired” only after it has received an input from theprevious modified full-rail differential logic circuit 200.

FIG. 3 shows one embodiment of a cascaded chain 301 of modifiedfull-rail differential logic circuits 300A, 300B, 300C and 300N of thepresent invention. Each modified full-rail differential logic circuit300A, 300B, 300C and 300N represents a stage in cascaded chain 301. Inone embodiment of the invention, each modified full-rail differentiallogic circuit 300A, 300B, 300C and 300N is similar to modified full-raildifferential logic circuit 200 discussed above with respect to FIG. 2.

As seen in FIG. 3, modified full-rail differential logic circuit 300Aincludes: a first clock input terminal 326A; a second clock inputterminal 327A; an out terminal 311A; and an outBar terminal 313A.

Modified full-rail differential logic circuit 300B includes: a firstclock input terminal 326B; a second clock input terminal 327B; an inputterminal 351B, coupled to out terminal 311A of modified full-raildifferential logic circuit 300A; an inputBar terminal 353B, coupled tooutBar terminal 313A of modified full-rail differential logic circuit300A; an output terminal 311B; and an outBar terminal 313B. Likewise,modified full-rail differential logic circuit 300C includes: a firstclock input terminal 326C; a second clock input terminal 327C; an inputterminal 351C, coupled to output terminal 311B of modified full-raildifferential logic circuit 300B; an inputBar terminal 353C, coupled tooutBar terminal 313B of modified full-rail differential logic circuit300B; an output terminal 311C; and an outBar terminal 313C.

Modified full-rail differential logic circuit 300N includes: a firstclock input terminal 326N; a second clock input terminal 327N; an inputterminal 351N, coupled to an output terminal 311N−1 (not shown) of amodified full-rail differential logic circuit 300N−1 (not shown); aninputBar terminal 353N, coupled to an outBar terminal 313N−1 (not shown)of a modified full-rail differential logic circuit 300N−1 (not shown);an output terminal 311N; and an outBar terminal 313N.

According to the invention, any number of modified full-raildifferential logic circuits 300A, 300B, 300C and 300N can be employedwith cascaded chain 301. As also shown in FIG. 3, and discussed above,output terminal 311A of modified full-rail differential logic circuit300A couples signal OUTA to input terminal 351B of modified full-raildifferential logic circuit 300B and outBar terminal 313A of modifiedfull-rail differential logic circuit 300A couples signal OUTBARA toinputBar terminal 353B of modified full-rail differential logic circuit300B. Likewise, output terminal 311B of modified full-rail differentiallogic circuit 300B couples signal OUTB to input terminal 351C ofmodified full-rail differential logic circuit 300C and outBar terminal313B of modified full-rail differential logic circuit 300B couplessignal OUTBARB to inputBar terminal 353C of modified full-raildifferential logic circuit 300C. In addition, output terminal 311N ofmodified full-rail differential logic circuit 300N couples signal OUTNto an input terminal 351N+1 (not shown) of a modified full-raildifferential logic circuit 300N+1 (not shown) and outBar terminal 313Nof modified full-rail differential logic circuit 300N couples signalOUTBARN to an inputBar terminal 353N+1 (not shown) of a modifiedfull-rail differential logic circuit 300N+1 (not shown).

According to the invention, each modified full-rail differential logiccircuit 300A, 300B, 300C and 30ON of cascaded chain 301 receives its owndelayed first clock signal CLKA 361, CLKB 371, CLKC 381 and CLKN 391,respectively. According to the invention clock signals CLKA 361, CLKB371, CLKC 381 and CLKN 391 are provided to modified full-raildifferential logic circuits 300A, 300B, 300C and 300N, respectively, byintroducing delay circuits 363, 373, 383 and 393 between successivemodified full-rail differential logic circuits 300A, 300B, 300C and300N. Consequently, delay circuit 363 introduces a delay time betweensignal CLKA 361, coupled to first clock input terminal 326A of modifiedfull-rail differential logic circuit 300A, and signal CLKB 371, coupledto first clock input terminal 326B of modified full-rail differentiallogic circuit 300B. Delay circuit 373 introduces a delay time betweensignal CLKB 371 and signal CLKC 381, coupled to first clock inputterminal 326C of modified full-rail differential logic circuit 300C. Twodelay circuits 363 and 373 introduce two delay times between signal CLKA361 and signal CLKC 381. Likewise, a series of N−1 delay circuits, andN−1 delay times, exists between signal CLKA 361 and signal CLKN 391,coupled to first clock input terminal 326N of modified full-raildifferential logic circuit 300N, and a further delay circuit 393introduces a further delay time between CLKN 391 and CLK N+1 (not shown)coupled to a first clock input terminal 326N+1 (not shown) of a modifiedfull-rail differential logic circuit 300N+1 (not shown).

Delay circuits 363, 373, 383 and 393 are any one of many delay circuitsknown in the art such as inverters, or groups of inverters, gates,transistors or any other elements that introduce a time delay. Accordingto the invention, delay circuits 363, 373, 383 and 393 are used toensure the activation of each stage, i.e., each modified full-raildifferential logic circuit 300A, 300B, 300C and 300N, is timed such thatthe delay of the clock is longer than the evaluation duration of theprevious stage. In one embodiment of 35 the invention, the delayed clocksignals CLKA 361, CLKB 371, CLKC 381 and CLKN 391 are timed to switchhigh (active) when the differential input voltage to modified full-raildifferential logic circuit 300A, 300B, 300C and 300N reaches apredetermined voltage level. The clock delay can be adjusted accordingto the predetermined differential voltage level required for robustnessand the specific needs of the circuit designer. This differentialvoltage level is typically a function of process and will vary fromcircuit to circuit and system to system.

In addition, according to the invention, each modified full-raildifferential logic circuit 300A, 300B, 300C and 300N of cascaded chain301 receives a second delayed clock signal at its second clock inputterminal 327A, 327B, 327C and 327N, respectively. In one embodiment ofthe invention, the second delayed clock signal for a given modifiedfull-rail differential logic circuit 300A, 300B, 300C and 300N ofcascaded chain 301 is the delayed clock signal of the following modifiedfull-rail differential logic circuit 300A, 300B, 300C and 300N incascaded chain 301. In this embodiment of the invention, the seconddelayed clock signal for a given modified full-rail differential logiccircuit 300A, 300B, 300C and 300N of cascaded chain 301 is provided bycoupling the second clock terminal 327A, 327B, 327C and 327N of a givenmodified full-rail differential logic circuit 300A, 300B, 300C and 300N,respectively, to the first clock input terminal 326B, 326C, 326D (notshown), 326N and 326N+1 (not shown) of the following stage 300B, 300C,30ON and 300N+1 (not shown).

Thus, in FIG. 3, line 320A couples second clock input terminal 327A ofmodified full-rail differential logic circuit 300A to first clock inputterminal 326B of modified full-rail differential logic circuit 300B anddelay circuit 363 introduces a delay time between signal CLKA 361,coupled to first clock input terminal 326A of modified full-raildifferential logic circuit 300A, and signal CLKB 371, coupled to secondclock input terminal 327A of modified full-rail differential logiccircuit 300A. Likewise, line 320B couples second clock input terminal327B of modified full-rail differential logic circuit 300B to firstclock input terminal 326C of modified full-rail differential logiccircuit 300C and delay circuit 373 introduces a delay time betweensignal CLKB 371, coupled to first clock input terminal 326B of modifiedfull-rail differential logic circuit 300B, and signal CLKC 381, coupledto second clock input terminal 327B of modified full-rail differentiallogic circuit 300B.

Similarly, line 320C couples second clock input terminal 327C ofmodified full-rail differential logic circuit 300C to first clock inputterminal 326D (not shown) of a modified full-rail differential logiccircuit 300D (not shown) and delay circuit 383 introduces a delay timebetween signal CLKC 381, coupled to first clock input terminal 326C ofmodified full-rail differential logic circuit 300C, and signal CLKD 382,coupled to second clock input terminal 327C of modified full-raildifferential logic circuit 300C. Likewise, line 320N couples first clockinput terminal 326N+1 (not shown) of a modified full-rail differentiallogic circuit 300N+1 (not shown) to second clock input terminal 327N ofmodified full-rail differential logic circuit 300N and delay circuit 393introduces a delay time between signal CLKN 391, coupled to first clockinput terminal 326N of modified full-rail differential logic circuit300N, and signal CLKN+1 392, coupled to second clock input terminal 327Nof modified full-rail differential logic circuit 300N.

In one embodiment of the invention, second clock input terminals 327A,327B, 327C and 327N of modified full-rail differential logic circuits300A, 300B, 300C and 300N, respectively, are coupled to a senseamplifiers (not shown in FIG. 3) in modified full-rail differentiallogic circuits 300A, 300B, 300C and 300N, such as sense amplifiercircuit 280 in FIG. 2, and the signals CLKB, CLKC, CLKD, and CLKN+1 areused as described above with respect to FIG. 2 to trigger the senseamplifiers (not shown in FIG. 3) in modified full-rail differentiallogic circuits 300A, 300B, 300C and 300N.

FIG. 4 is one embodiment of a timing diagram for cascaded chain 301 ofmodified full-rail differential logic circuits 300A, 300B, 300C, and300N of FIG. 3. As seen in FIG. 3 and FIG. 4 together, according to oneembodiment of the invention, at time T0, i.e., point T0 400A in FIG. 4:signal CLKA 461 begins to go high; OUTA 411A at out terminal 311A ishigh; OUTBARA 413A is high; CLKB 471 is low; OUTB 411B is high; OUTBARB413B is high; CLKC 481 is low; OUTC is high; OUTBARC is high; and CLKD491 is low.

A delay time 462 from point T0 400A and to point T1 400B is introducedby delay circuit 363. As discussed above, delay time 462 helps ensuremodified full-rail differential logic circuit 300B receives signals OUTAand OUTBARA from modified full-rail differential logic circuit 300Abefore the switching of signal CLKB 471. As also discussed above,according to the invention, CLKB 471 also acts as the delayed clocksignal to second clock input terminal 327A of modified full-raildifferential logic circuit 300A to serve as a trigger for a senseamplifier circuit, such as sense amplifier circuit 280 of FIG. 2, thatis used in modified full-rail differential logic circuit 300A.

At time T1, i.e., point T1 400B in FIG. 4: signal CLKA 461 continues togo high; OUTA 411A starts to slowly go low at point 466; signal OUTBARAat outBar terminal 313A remains high; CLKB 471 starts to go high; OUTB411B remains high; OUTBARB 413B remains high; CLKC 481 remains low; OUTCremains high; OUTBARC remains high; and CLKD 491 remains low.

A delay time 472 from point T1 400B and to point T2 400C is introducedby delay circuit 373. As discussed above, delay time 472 helps ensuremodified full-rail differential logic circuit 300C receives signals OUTBand OUTBARB from modified full-rail differential logic circuit 300Bbefore the switching of signal CLKC 481. As also discussed above,according to the invention, CLKC 481 also acts as the delayed clocksignal to second clock input terminal 327B of modified full-raildifferential logic circuit 300B to serve as a trigger for a senseamplifier circuit, such as sense amplifier circuit 280 of FIG. 2, thatis used in modified full-rail differential logic circuit 300B.

At time T2, i.e., point T2 400C in FIG. 4: signal CLKA 461 reaches highpoint 463; the sense amplifier, such as sense amplifier 280 in FIG. 2,which, according to the invention, is part of modified full-raildifferential logic circuit 300A is activated and Output OUTA 411A pullsstrongly low starting at point 467, note the difference in the slope ofsignal OUTA 411A between points 466 and 467, when the sense amplifier isnot activated, and points 467 and 468, when the sense amplifier isactivated; OUTBARA remains high; CLKB 471 continues to go high; OUTB411B begins to slowly go low at point 476; OUTBARB 413B remains high;CLKC 481 starts to go high; OUTC remains high; OUTBARC remains high; andCLKD 491 remains low.

A delay time 482 from point T2 400C and to point T3 400D is introducedby delay circuit 383. As discussed above, delay time 482 helps ensuremodified full-rail differential logic circuit 300D (not shown) receivessignals OUTC and OUTBARC from modified full-rail differential logiccircuit 300C before the switching of signal CLKD 491. As also discussedabove, according to the invention, CLKC 491 also acts as the delayedclock signal to second clock input terminal 327C of modified full-raildifferential logic circuit 300C to serve as a trigger for a senseamplifier circuit, such as sense amplifier circuit 280 of FIG. 2, thatis used in modified full-rail differential logic circuit 300C.

At time T3, i.e., point T3 400D in FIG. 4: signal CLKA remains high;OUTA reaches low point 468; OUTBARA remains high; CLKB 471 reaches highpoint 473; the sense amplifier, such as sense amplifier 280 in FIG. 2,which, according to the invention, is part of modified full-raildifferential logic circuit 300B is activated and Output OUTB 411B pullsstrongly low starting at point 477, note the difference in the slope ofsignal OUTB 411B between points 476 and 477, when the sense amplifier isnot activated, and points 477 and 478, when the sense amplifier isactivated; CLKC 481 continues to go high; OUTC begins to slowly go lowat point 486; OUTBARC remains high; and CLKD 491 begins to go high. Asdiscussed above, according to the invention, any number of modifiedfull-rail differential logic circuits 300A, 300B, 300C and 300N can beemployed with cascaded chain 301. In addition, the process discussedabove will repeat for each switching of the system clock. Those of skillin the art will further recognize that the choice of signal highs andsignal lows was made arbitrarily in FIG. 4 for illustrative purposesonly and that at other times, and in other embodiments of the invention,signal highs could be replaced with signal lows and vice-versa.

As discussed above, modified full-rail differential logic circuits 200,300A, 300B, 300C and 300N of the invention include sense amplifiercircuit 280 that is triggered by the delayed clock of the followingstage, i.e., the clock input to the sense amplifier circuit of themodified full-rail differential logic circuits of the invention isadditionally delayed with respect to the delayed clock that drives thefull-rail differential logic. The addition of the sense amplifiercircuit, and second delayed clock signal, according to the invention,allows the sense amplifier circuit to act as the driver and thereforethere is no need for increasing the size of the logic network to providethe driver function. Consequently, the modified full-rail differentiallogic circuits of the invention are capable of operating efficientlyunder heavy load conditions without the increased size and thesignificant reduction in speed associated with prior art full-raildifferential logic circuits. In addition, the modified full-raildifferential logic circuits of the invention require less space, aresimpler, dissipate less heat and have fewer components to potentiallyfail.

As also discussed above, the modified full-rail differential logiccircuits of the invention can be cascaded together to form the chainscommonly used in the industry. When the modified full-rail differentiallogic circuits of the invention are cascaded together, the advantages ofthe modified full-rail differential logic circuits of the invention areparticularly evident and the gains in terms of efficiency, sizereduction and flexibility are further pronounced.

The foregoing description of an implementation of the invention has beenpresented for purposes of illustration and description only, andtherefore is not exhaustive and does not limit the invention to theprecise form disclosed. Modifications and variations are possible inlight of the above teachings or may be acquired from practicing theinvention.

For example, for illustrative purposes specific embodiments of theinvention were shown with specific transistors. However, the NFETs andPFETS shown in the figures can be readily exchanged for PFETs and NFETsby reversing the polarities of the supply voltages or by other wellknown circuit modifications.

Consequently, the scope of the invention is defined by the claims andtheir equivalents.

What is claimed is:
 1. A cascaded chain of modified full-raildifferential logic circuits comprising: a first supply voltage; a secondsupply voltage; a first modified full-rail differential logic circuit,said first modified full-rail differential logic circuit comprising: afirst modified full-rail differential logic circuit out terminal; afirst modified full-rail differential logic circuit outBar terminal; afirst modified full-rail differential logic circuit first node, saidfirst modified full-rail differential logic circuit first node beingcoupled to said first supply voltage; a first transistor, said firsttransistor comprising a first transistor first flow electrode, a firsttransistor second flow electrode and a first transistor controlelectrode, said first modified full-rail differential logic circuitfirst node being coupled to said first transistor first flow electrode,said first transistor second flow electrode being coupled to said firstmodified full-rail differential logic circuit out terminal; a secondtransistor, said second transistor comprising a second transistor firstflow electrode, a second transistor second flow electrode and a secondtransistor control electrode, said first modified full-rail differentiallogic circuit first node being coupled to said second transistor firstflow electrode, said second transistor second flow electrode beingcoupled to said first modified full-rail differential logic circuitoutBar terminal; a third transistor, said third transistor comprising athird transistor first flow electrode, a third transistor second flowelectrode and a third transistor control electrode, said firsttransistor control electrode being coupled to said third transistorfirst flow electrode and said first modified full-rail differentiallogic circuit outBar terminal, said second transistor control electrodebeing coupled to said third transistor second flow electrode and saidfirst modified full-rail differential logic circuit out terminal; afourth transistor, said fourth transistor comprising a fourth transistorfirst flow electrode, a fourth transistor second flow electrode and afourth transistor control electrode; said fourth transistor first flowelectrode being coupled to said first modified full-rail differentiallogic circuit first node, said fourth transistor second flow electrodebeing coupled to said first modified full-rail differential logiccircuit out terminal, said fourth transistor control electrode beingcoupled to a first clock signal; a fifth transistor, said fifthtransistor comprising a fifth transistor first flow electrode, a fifthtransistor second flow electrode and a fifth transistor controlelectrode; said fifth transistor first flow electrode being coupled tosaid first modified full-rail differential logic circuit first node,said fifth transistor second flow electrode being coupled to said firstmodified full-rail differential logic circuit outBar terminal, saidfifth transistor control electrode being coupled to said first clocksignal; a first modified full-rail differential logic circuit senseamplifier circuit coupled between said first modified full-raildifferential logic circuit out terminal and said first modifiedfull-rail differential logic circuit outBar terminal, said firstmodified full-rail differential logic circuit sense amplifier circuithaving an input terminal coupled to a second clock signal; a logicblock, said logic block comprising: at least one logic block inputterminal; a logic block out terminal; and a logic block outBar terminal,said logic block out terminal being coupled to said first modifiedfull-rail differential logic circuit out terminal and said logic blockoutBar terminal being coupled to said first modified full-raildifferential logic circuit outBar terminal; a second modified full-raildifferential logic circuit, said second modified full-rail differentiallogic circuit comprising: a second modified full-rail differential logiccircuit out terminal; a second modified full-rail differential logiccircuit outBar terminal; a second modified full-rail differential logiccircuit first node, said second modified full-rail differential logiccircuit first node being coupled to said first supply voltage; a firsttransistor, said first transistor comprising a first transistor firstflow electrode, a first transistor second flow electrode and a firsttransistor control electrode, said second modified full-raildifferential logic circuit first node being coupled to said firsttransistor first flow electrode, said first transistor second flowelectrode being coupled to said second modified full-rail differentiallogic circuit out terminal; a second transistor, said second transistorcomprising a second transistor first flow electrode, a second transistorsecond flow electrode and a second transistor control electrode, saidsecond modified full-rail differential logic circuit first node beingcoupled to said second transistor first flow electrode, said secondtransistor second flow electrode being coupled to said second modifiedfull-rail differential logic circuit outBar terminal; a thirdtransistor, said third transistor comprising a third transistor firstflow electrode, a third transistor second flow electrode and a thirdtransistor control electrode, said first transistor control electrodebeing coupled to said third transistor first flow electrode and saidsecond modified full-rail differential logic circuit outBar terminal,said second transistor control electrode being coupled to said thirdtransistor second flow electrode and said second modified full-raildifferential logic circuit out terminal; a fourth transistor, saidfourth transistor comprising a fourth transistor first flow electrode, afourth transistor second flow electrode and a fourth transistor controlelectrode; said fourth transistor first flow electrode being coupled tosaid second modified full-rail differential logic circuit first node,said fourth transistor second flow electrode being coupled to saidsecond modified full-rail differential logic circuit out terminal, saidfourth transistor control electrode being coupled to said second clocksignal; a fifth transistor, said fifth transistor comprising a fifthtransistor first flow electrode, a fifth transistor second flowelectrode and a fifth transistor control electrode; said fifthtransistor first flow electrode being coupled to said second modifiedfull-rail differential logic circuit first node, said fifth transistorsecond flow electrode being coupled to said second modified full-raildifferential logic circuit outBar terminal, said fifth transistorcontrol electrode being coupled to said second clock signal; a secondmodified full-rail differential logic circuit sense amplifier circuitcoupled between said second modified full-rail differential logiccircuit out terminal and said second modified full-rail differentiallogic circuit outbar terminal, said second modified full-raildifferential logic circuit sense amplifier circuit having an inputterminal coupled to a third clock signal; a logic block, said logicblock comprising: at least one logic block input terminal; a logic blockout terminal; and a logic block outBar terminal, said logic block outterminal being coupled to said second modified full-rail differentiallogic circuit out terminal and said logic block outBar terminal beingcoupled to said second modified full-rail differential logic circuitoutBar terminal, wherein; said second clock signal is delayed withrespect to said first clock signal by a predetermined delay time andsaid third clock signal is delayed with respect to said second clocksignal by a predetermined delay time.
 2. The cascaded chain of modifiedfull-rail differential logic circuits of claim 1, wherein; said firstmodified full-rail differential logic circuit sense amplifier circuitcomprises: a sixth transistor, said sixth transistor comprising a sixthtransistor first flow electrode, a sixth transistor second flowelectrode and a sixth transistor control electrode, said firsttransistor second flow electrode being coupled to said sixth transistorfirst flow electrode, said sixth transistor second flow electrode beingcoupled to a first modified full-rail differential logic circuit secondnode, said sixth transistor control electrode being coupled to saidthird transistor first flow electrode and said first modified full-raildifferential logic circuit outBar terminal; a seventh transistor, saidseventh transistor comprising a seventh transistor first flow electrode,a seventh transistor second flow electrode and a seventh transistorcontrol electrode, said second transistor second flow electrode beingcoupled to said seventh transistor first flow electrode, said seventhtransistor second flow electrode being coupled to said first modifiedfull-rail differential logic circuit second node, said seventhtransistor control electrode being coupled to said third transistorsecond flow electrode and said first modified full-rail differentiallogic circuit out terminal; an eighth transistor, said eighth transistorcomprising an eighth transistor first flow electrode, an eighthtransistor second flow electrode and an eighth transistor controlelectrode, said eighth transistor first flow electrode being coupled tosaid first modified full-rail differential logic circuit second node,said eighth transistor second flow electrode being coupled to saidsecond supply voltage, said eighth transistor control electrode beingcoupled to receive said second clock signal, further wherein; said asecond modified full-rail differential logic circuit sense amplifiercircuit comprises: a sixth transistor, said sixth transistor comprisinga sixth transistor first flow electrode, a sixth transistor second flowelectrode and a sixth transistor control electrode, said firsttransistor second flow electrode being coupled to said sixth transistorfirst flow electrode, said sixth transistor second flow electrode beingcoupled to a second modified full-rail differential logic circuit secondnode, said sixth transistor control electrode being coupled to saidthird transistor first flow electrode and said second modified full-raildifferential logic circuit outBar terminal; a seventh transistor, saidseventh transistor comprising a seventh transistor first flow electrode,a seventh transistor second flow electrode and a seventh transistorcontrol electrode, said second transistor second flow electrode beingcoupled to said seventh transistor first flow electrode, said seventhtransistor second flow electrode being coupled to said second modifiedfull-rail differential logic circuit second node, said seventhtransistor control electrode being coupled to said third transistorsecond flow electrode and said second modified full-rail differentiallogic circuit out terminal; an eighth transistor, said eighth transistorcomprising an eighth transistor first flow electrode, an eighthtransistor second flow electrode and an eighth transistor controlelectrode, said eighth transistor first flow electrode being coupled tosaid second modified full-rail differential logic circuit second node,said eighth transistor second flow electrode being coupled to saidsecond supply voltage, said eighth transistor control electrode beingcoupled to receive said third clock signal.
 3. The cascaded chain ofmodified full-rail differential logic circuits of claim 1, wherein; saidlogic block of said first modified full-rail differential logic circuitand said logic block of said second modified full-rail differentiallogic circuit comprise differential logic.
 4. The cascaded chain ofmodified full-rail differential logic circuits of claim 1, wherein; saidlogic block of said first modified full-rail differential logic circuitand said logic block of said second modified full-rail differentiallogic circuit comprise differential logic gates.
 5. The cascaded chainof modified full-rail differential logic circuits of claim 1, wherein;said logic block of said first modified full-rail differential logiccircuit and said logic block of said second modified full-raildifferential logic circuit comprise NMOS pass transistor logic; saidlogic block of said first modified full-rail differential logic circuitcomprises at least one control variable input and at least one passvariable input; and said logic block of said second modified full-raildifferential logic circuit comprises at least one control variable inputand at least one pass variable input.
 6. The cascaded chain of modifiedfull-rail differential logic circuits of claim 1, wherein; said firstsupply voltage is Vdd and said second supply voltage is ground.
 7. Thecascaded chain of modified full-rail differential logic circuits ofclaim 6, wherein; said first transistor, said second transistor, saidfourth transistor and said fifth transistor of said first modifiedfull-rail differential logic circuit and said first transistor, saidsecond transistor, said fourth transistor and said fifth transistor ofsaid second modified full-rail differential logic circuit are PFETs. 8.The cascaded chain of modified full-rail differential logic circuits ofclaim 7, wherein; said third transistor, said sixth transistor, saidseventh transistor and said eighth transistor of said first modifiedfull-rail differential logic circuit and said third transistor, saidsixth transistor, said seventh transistor and said eighth transistor ofsaid second modified full-rail differential logic circuit are NFETs. 9.A modified full-rail differential logic circuit comprising: a firstsupply voltage; a second supply voltage; a modified full-raildifferential logic circuit out terminal; a modified full-raildifferential logic circuit outBar terminal; a modified full-raildifferential logic circuit first node, said modified full-raildifferential logic circuit first node being coupled to said first supplyvoltage; a first transistor, said first transistor comprising a firsttransistor first flow electrode, a first transistor second flowelectrode and a first transistor control electrode, said modifiedfull-rail differential logic circuit first node being coupled to saidfirst transistor first flow electrode, said first transistor second flowelectrode being coupled to said modified full-rail differential logiccircuit out terminal; a second transistor, said second transistorcomprising a second transistor first flow electrode, a second transistorsecond flow electrode and a second transistor control electrode, saidmodified full-rail differential logic circuit first node being coupledto said second transistor first flow electrode, said second transistorsecond flow electrode being coupled to said modified full-raildifferential logic circuit outbar terminal; a third transistor, saidthird transistor comprising a third transistor first flow electrode, athird transistor second flow electrode and a third transistor controlelectrode, said first transistor control electrode being coupled to saidthird transistor first flow electrode and said modified full-raildifferential logic circuit outBar terminal, said second transistorcontrol electrode being coupled to said third transistor second flowelectrode and said modified full-rail differential logic circuit outterminal; a fourth transistor, said fourth transistor comprising afourth transistor first flow electrode, a fourth transistor second flowelectrode and a fourth transistor control electrode; said fourthtransistor first flow electrode being coupled to said modified full-raildifferential logic circuit first node, said fourth transistor secondflow electrode being coupled to said modified full-rail differentiallogic circuit out terminal, said fourth transistor control electrodebeing coupled a first clock signal; a fifth transistor, said fifthtransistor comprising a fifth transistor first flow electrode, a fifthtransistor second flow electrode and a fifth transistor controlelectrode; said fifth transistor first flow electrode being coupled tosaid modified full-rail differential logic circuit first node, saidfifth transistor second flow electrode being coupled to said modifiedfull-rail differential logic circuit outBar terminal, said fifthtransistor control electrode being coupled said first clock signal; amodified full-rail differential logic circuit sense amplifier circuitcoupled between said modified full-rail differential logic circuit outterminal and said modified full-rail differential logic circuit outBarterminal, said modified full-rail differential logic circuit senseamplifier circuit having an input terminal coupled to a second clocksignal; a logic block, said logic block comprising: at least one logicblock input terminal; a logic block out terminal; and a logic blockoutBar terminal, said logic block out terminal being coupled to saidmodified full-rail differential logic circuit out terminal and saidlogic block outBar terminal being coupled to said modified full-raildifferential logic circuit outBar terminal, wherein; said second clocksignal is delayed with respect to said first clock signal by apredetermined time.
 10. The modified full-rail differential logiccircuit of claim 9, wherein; said modified full-rail differential logiccircuit sense amplifier circuit comprises: a sixth transistor, saidsixth transistor comprising a sixth transistor first flow electrode, asixth transistor second flow electrode and a sixth transistor controlelectrode, said first transistor second flow electrode being coupled tosaid sixth transistor first flow electrode, said sixth transistor secondflow electrode being coupled to a modified full-rail differential logiccircuit second node, said sixth transistor control electrode beingcoupled to said third transistor first flow electrode and said modifiedfull-rail differential logic circuit outBar terminal; a seventhtransistor, said seventh transistor comprising a seventh transistorfirst flow electrode, a seventh transistor second flow electrode and aseventh transistor control electrode, said second transistor second flowelectrode being coupled to said seventh transistor first flow electrode,said seventh transistor second flow electrode being coupled to saidmodified full-rail differential logic circuit second node, said seventhtransistor control electrode being coupled to said third transistorsecond flow electrode and said modified full-rail differential logiccircuit out terminal; an eighth transistor, said eighth transistorcomprising an eighth transistor first flow electrode, an eighthtransistor second flow electrode and an eighth transistor controlelectrode, said eighth transistor first flow electrode being coupled tosaid modified full-rail differential logic circuit second node, saideighth transistor second flow electrode being coupled to said secondsupply voltage, said eighth transistor control electrode being coupledto receive said second clock signal.
 11. The modified full-raildifferential logic circuit of claim 10, wherein; said logic block ofsaid modified full-rail differential logic circuit comprisesdifferential logic.
 12. The modified full-rail differential logiccircuit of claim 10, wherein; said logic block of said modifiedfull-rail differential logic circuit comprises differential logic gates.13. The modified full-rail differential logic circuit of claim 10,wherein; said logic block of said modified full-rail differential logiccircuit comprises NMOS pass transistor logic; and said logic block ofsaid modified full-rail differential logic circuit includes at least onecontrol variable input and at least one pass variable input.
 14. Themodified full-rail differential logic circuit of claim 10, wherein; saidfirst supply voltage is Vdd and said second supply voltage is ground.15. The modified full-rail differential logic circuit of claim 14,wherein; said first transistor, said second transistor, said fourthtransistor and said fifth transistor are PFETs.
 16. The modifiedfull-rail differential logic circuit of claim 15, wherein; said thirdtransistor, said sixth transistor, said seventh transistor and saideighth transistor are NFETs.